Most satellite communication and navigation systems transmit signals using circularly polarized (CP) waves to benefit from the advantages that CP waves offer. Circularly polarized antennas having good axial ratio (AR) over the operating frequency band and over a wide half-power beamwidth (HPBW) are then required to establish and maintain satellite links from any location on Earth. In particular, the navigation applications using any satellite navigation systems (SNS) need antennas exhibiting an excellent AR over a wide frequency band (or multiple bands) and over a wide beamwidth to overcome low horizon signal reception.
Some of the prior art antennas that meet some of these requirements are: (1) the printed stacked patch antenna, (2) the cross printed dipole, and (3) the Folded Printed Quadrifilar Helical Antenna (FPQHA).
Dielectric Resonator Antennas (DRAs) offer high-radiation efficiency, a high degree of flexibility, and have inherently a wide operating bandwidth. In addition, compact antennas based on dielectric resonators are achievable by optimizing the width to height ratio or using high permittivity material. However, in the prior art, little attention has been given to multi-band and wideband circularly polarized DRA designs.
A more recent approach to improve the bandwidth of DRA antennas consists of combining two radiating bands, one using the dielectric resonator and one using the feed network. In this case, the feed network is performing a dual function: providing feeding to the DRA and also radiating on its own, but at a predefined band. Such an antenna is referred to as a hybrid dielectric resonator antenna. This type of antenna can have a very wide bandwidth while maintaining its radiation characteristics over the operating frequency band.
Several techniques have been proposed to generate CP when using DRAs. The different techniques can be classified into two categories: (1) single probe feed, and (2) multiple probe feed. Single probe feed schemes generally do not achieve AR bandwidth as wide as multiple probe feed. Their frequency bandwidth is usually limited to a few percent. By contrast, multiple probe configurations allow broad AR bandwidth, in the range of 20%.
In the prior art, Leung et al. disclose that DRA designs fed by conformal lines are interesting solutions to generate CP over a wide bandwidth [K. W. Leung, W. C. Wong, K. M. Luk, and E. K. N. Yung, “Circular-polarised dielectric resonator antenna excited by dual conformal strips,” Electron. Lett., vol. 36, no. 6, pp. 484-486, March 2000]. However, the bandwidth obtained here is not sufficient to cover the 32.2% bandwidth including all the SNS, from 1.16 to 1.61 GHz. Buerkle et al. also presented a dual-band DRA achieving a bandwidth over 25% [A. Buerkle, K. Sarabandi, H. Mosallaei, “Compact Slot and Dielectric Resonator Antenna With Dual-Resonance, Broadband Characteristics,” IEEE Trans. Antennas and Propag., vol. 53, no. 3, pp. 1020-1027, March 2005].
Based on the aforementioned shortcomings of the prior art, the present invention seeks to provide an improved hybrid DRA design.